harmonicFunction. maps between RN figures and function labels

[MarkGotham]

Resolves #1103

[coveralls]

Coverage increased (+0.004%) to 93.1% when pulling 7741097 on MarkGotham:harmonicFunction into 33b37c4 on cuthbertLab:master.

[MarkGotham]

#1103

[mscuthbert]

Thanks for the contribution Mark -- I think I really do want them to be Enums -- we're moving that way throughout the system. They can have a str() form that turns them into the labels here, but I'm trying to create more ways that people can see what the possible choices are and what they mean. Sort of like we did with the various #6, #7 Enums in RomanText.

[mscuthbert]

A few comments and requested changes before looking more closely at the code.

The code should also use English where possible. Only in a few cases where there is no commonly used English equivalent ("Hauptstimme", "Augenmusik") should German or French ("jetté") be used. Italian is sort of grandfathered in...

[jacobtylerwalls]

Thanks Mark, I left a few comments. Myke may be hoping to merge #1298 before this, so there might be a mypy tweak to do when that's in.

[mscuthbert]

Thanks. Great work.